An efficient cover on a MSW landfill’s body and a good biogas collection system are not enough to guarantee the absence of uncontrolled gas flux from the surface, both during the operative and in the post-closure phases.

The monitoring of diffuse emissions from a landfill body is a crucial process that can provide information about:

Landfill management: functioning of the biogas collection system, identification of areas with higher soil biogas emission, and presence of fractures on the cover and consequent leakage

The diffuse biogas emission from the landfill body is measured by means of the accumulation chamber technique, which allows a direct, timely and inexpensive quantification of the gas flux.

Such procedures involve geo-referenced flux measurements, on a regular grid, of the entire landfill body. A further processing of the acquired data by geo-statistical methods allows the creation of isoflux maps in relation to the various measured contaminants and the quantification of the total biogas emission from the landfill body. These maps, showing the spatial distribution of soil biogas emissions, play a fundamental role in the planning of every management intervention such as:

Biogas collection

coverage of the landfill body

identification of areas with anomalous degassing activity

efficiency of the anaerobic digester

calibration of the production model.

The instrument used to perform the measurements on site is a flux-meter, designed and produced by West Systems, based on the static non-stationary technique. The flux-meter performs real-timemeasurements of the gas concentrations inside the accumulation chamber allowing an immediate assessment of growth rates. The obtained results are reliable regardless of the knowledge of soil composition and flux regime.

The reliability of global emission estimates is given by the comparison between these results and the measurements carried out by the landfill management.